1. Field of the Invention
The invention relates to anti-cancer applications using immunomers as therapeutic agents.
2. Summary of the Related Art
Recently, several researchers have demonstrated the validity of the use of oligonucleotides as immunostimulatory agents in immunotherapy applications. The observation that phosphodiester and phosphorothioate oligonucleotides can induce immune stimulation has created interest in developing these compounds as a therapeutic tool. These efforts have focused on phosphorothioate oligonucleotides containing the natural dinucleotide CpG. Kuramoto et al., Jpn. J. Cancer Res. 83:1128-1131 (1992) teaches that phosphodiester oligonucleotides containing a palindrome that includes a CpG dinucleotide can induce interferon-alpha and gamma synthesis and enhance natural killer activity. Krieg et al., Nature 371:546-549 (1995) discloses that phosphorothioate CpG-containing oligonucleotides are immunostimulatory. Liang et al., J. Clin. Invest. 98:1119-1129 (1996) discloses that such oligonucleotides activate human B cells. Moldoveanu et al., Vaccine 16:1216-124 (1998) teaches that CpG-containing phosphorothioate oligonucleotides enhance immune response against influenza virus. McCluskie and Davis, J. Immunol. 161:4463-4466 (1998) teaches that CpG-containing oligonucleotides act as potent adjuvants, enhancing immune response against hepatitis B surface antigen.
Other modifications of CpG-containing phosphorothioate oligonucleotides can also affect their ability to act as modulators of immune response. See, e.g., Zhao et al., Biochem. Pharmacol. (1996) 51:173-182; Zhao et al., Biochem Pharmacol. (1996) 52:1537-1544; Zhao et al., Antisense Nucleic Acid Drug Dev. (1997) 7:495-502; Zhao et al., Bioorg. Med. Chem. Lett. (1999) 9:3453-3458; Zhao et al., Bioorg. Med. Chem. Lett. (2000) 10:1051-1054; Yu et al., Bioorg. Med. Chem. Lett. (2000) 10:2585-2588; Yu et al., Bioorg. Med. Chem. Lett. (2001) 11:2263-2267; and Kandimalla et al., Bioorg. Med. Chem. (2001) 9:807-813. U.S. Pat. No. 6,426,334 shows the promise of these compounds as anti-cancer agents.
Although it has been well demonstrated that many murine and human tumors carry immunogenic epitopes that can be recognized by the host immune system, in most cases host defenses fail to mount an appropriate response causing uncontrolled tumor growth in cancer patients. The failure of the host immune system to elicit defense against tumor cells could be related to low immunogenic nature of tumor antigens and/or defects in the host immune system itself.
These reports make clear that there remains a need to be able to enhance the anticancer activity of immunostimulatory oligonucleotides.